1. Field of the Invention
The present invention relates to a combustion state detecting apparatus for an internal combustion engine, in particular, to a combustion state detecting apparatus for an internal combustion engine, which detects a change in the amount of ions generated at the time of combustion in the internal combustion engine to detect a combustion state in the internal combustion engine.
2. Description of the Related Art
Recently, environmental conservation and fuel exhaustion problems have been raised. Even for the automobile industry, a response to the above-mentioned problems is a big issue.
Although a large number of technologies for maximizing the efficiency of an internal combustion engine have been developed as countermeasures against the above-mentioned problems, it is necessary to know a combustion state to maximize the efficiency of the internal combustion engine. Therefore, there is a rapidly growing need for an apparatus capable of detecting the combustion state.
As a conventional apparatus capable of detecting the combustion state, for example, an apparatus described in JP 3753290 B (hereinafter, referred to as Patent Document 1) has been proposed. The apparatus described in Patent Document 1 detects ions generated according to the combustion in a combustion chamber in the form of current, and uses the detected ion current to determine the combustion state.
In order to detect the ion current, a high voltage is required to be applied to a detection probe provided in the combustion chamber. As means of generating the high voltage, a Zener diode and a capacitor are used.
As described in Patent Document 1, the Zener diode and the capacitor are connected to the low voltage side of a secondary winding of an ignition coil. However, since correspondingly large withstand voltage and capacity are required, the Zener diode and the capacitor become large in size as components. In addition, correspondingly high cost is required. Therefore, there is a problem in that the Zener diode and the capacitor prevent the size and cost of the apparatus from being reduced.